CONTRAST SENSITIVITY (CHARTS)

Jagdish Dukre

no international recommendation on how contrast of visual acuity charts should be defined.

Therefore there are differences in the contrast of tests of different manufacturers.

Test results are marked on the recording sheet at the level used (see example below) going along that level toward the right until the visual acuity value, measured at that contrast (A’ at 1.2%, B’ at 2.5%), is reached.

If the person’s visual acuity was 20/20 (6/6, 1.0), the line connecting these three points, A’, B’ and X, depicts the slope of the contrast sensitivity curve of this person.

Cambridge low contrast gratings It is a rapid and simple screening test for contrast

sensitivity. Performed at a distance of 6m. It comprises of 12 pair of plates consisting of

stripes of varying contrast. First one is for demonstration and rest are for the

proper testing and are numbered from 1-10. The plates are changed sequentially starting from

plate 1 till the patient fails to respond.

Cambridge low contrast gratings Then a new series is begun starting 4 plates prior to

where the patient failed to respond.

Four such series are completed and the score of each series is noted (numbered as per the number of plate read) and added.

The final total value is converted into contrast sensitivity from the provided table.

Functional Acuity Contrast Testing (FACT)

FACT charts were developed by Dr. Arthur Ginsburg.

FACT comprises of a chart with sine-wave gratings of varying contrast as well as varying spatial frequencies.

It is an accurate and comprehensive grating chart that tests functional visual acuity.

This test is performed at a distance of 10 feet.

The chart tests five spatial frequencies (sizes) and nine levels of contrast.

The Contrast varies in a row, decrease from left to right. And the spatial frequencies increase as one move down the

various columns from top to bottom

The patient determines the last grating seen for each row (A, B, C, D and E) and reports the orientation of the grating: right, up or left.

The last correct grating seen for each spatial frequency is plotted on a contrast sensitivity curve.

Vistech VCTS 6000 and 6500 Contrast Sensitivity Tests

There are two Vistech CS tests; model 6000 is used to test near (i.e., reading distance) sensitivity at 40 cm (16 in), and model 6500 tests far sensitivity (3.05 m = 10 ft).

Both tests use charts with 5 rows of sine-wave gratings. The rows increase in spatial frequency from the top to

bottom of the chart, and on each row the gratings decrease in contrast from left to right.

Vistech VCTS 6000 and 6500 Contrast Sensitivity Tests

The observer’s task is to indicate each grating's orientation (leaning left, vertical or leaning right);

The lowest contrast grating determines the sensitivity score for that spatial frequency.

The sensitivity at each spatial frequency can be used to plot a csf for the observer, and can also be compared to the age norms provided for the test.

Vistech VCTS 6000 and 6500 Contrast Sensitivity Tests

CSV-1000E It is widely used in the

world

This test provides four rows of sine-wave gratings

The test distant 2.5 meters,

Gratings test the spatial frequencies of 3,7,12,and 18 cycles/degree

$250.00

CSV-1000E Useful for the evaluation of ocular disease

(particularly cataracts, glaucoma, optic neuritis, diabetes, and macular degeneration), contact lenses, and refractive surgery.

For cataract documentation, a functional acuity score can be obtained directly from the test scoring sheet.

$250.00

CSV-1000-S This test presents standard visual acuity from

20/15 to 20/200, two rows of spatial frequencies (6 and 12 cycles/degree) and a real-world driver’s scene.

$250.00

CSV-1000-S Used for in or out of office screening and for

cataract evaluation The test is very useful for cataract

documentation as it provides a standard acuity score, a functional acuity score and a real-world simulation.

$250.00

CSV-1000 LAN C

Provided the same tests as standard CSV-1000-S expect that acuity is presented in landolt c format

Useful when patient cant read English alphabet

CSV-1OOORS The CSV-1000RS test face is used

widely for screening refractive surgery patients.

The test presents ETDRS LogMAR acuity from 20/10 to 20/100 and one row of spatial frequency at 12 cycles/degree.

The patient can be easily screened in the examination chair for ETDRS acuity and contrast sensitivity.

If a contrast sensitivity deficit is found, retesting the patient with all four spatial frequencies using the CSV-1000E is recommended.

CSV-1000 CVA

Used to evaluate both contrast sensitivity and low contrast acuity

Contain 3 contrast levels

CSV -1000 – 1.5 cpd

It is special test designed specifically for food and drug administration clinical trials

Recommended test distance of 8 feet,

The gratings test one spatial frequency of 1.5 cycles/degree.

$250.00

Contrast sensitivity view in testers

Sine-wave grating contrast sensitivity testing is available in view-in testers

The advantages are that they eliminate the need to control room light levels and can be used in small test space

Pell i -robson letter contrast sensit ivity

It is simply of quickly measured and provides a reliable measurement of low spatial frequency contrast sensitivity ( 0.5 – 2 cycles)

Method: Sit the patient 1m from the chart with his or her

correction if needs Occlude one eye or with both eye With both eyes result high with 0.15 log units

The patient is asked to read the alphabets starting from left hand corner,

when he fails to respond several seconds are given to him to retry and guess the alphabet.

The score of the test is recorded by the faintest triplet out of which at least 2 letters are correctly identified.

The log CS value for this triplet is given by the number on the scoring pad nearest to the triplet, either on the left or the right side.

Record the contrast sensitivity score in log units

Results:Results: For patient 20-50 years old monocular contrast

sensitivity should be 1.80 log unit Patient less than 20 years and older so years

monocular contrast sensitivity should be 1.65 log units

Most common errors

Not allowing patient at least 20 second for letters to become visible

Not pushing patient to guess

Illumination is poor

Mars Perceptrix Letter Contrast Test The Mars Perceptrix contrast test indicates the

lowest contrasts your patients can perceive.

With the Mars test, it is the contrast, and not the letter size, which diminishes from the beginning to the end of the chart.

The letters are large, insuring that most patients, even those with low vision, can see them.

The Mars Perceptrix test comes with 3 low contrast charts, instructions and storage pouch.

Mars Perceptrix Letter Contrast Test

$395.00

$150.00 each

Mars Perceptrix Numbers Contrast Chart

$150.00 each

$395.00

Adult Near Contrast Test This adult near vision low contrast test features

both ETDRS Format and Continuous Text in 100%, 25%, 10%, 5%, and 2.5% contrast level.

Continuous text letter sizes range from 6/30 to 6/6 equivalent in each contrast level.

ETDRS format letters sizes range from 6/120 to 6/3 equivalent in 17 increments for each contrast level.

The near vision contrast booklet contains 7 pages measuring 15.8 cm x 15.8 cm.

testing distance : 40 cm

$140.00

Sloan Letter Low Contrast Fl ip Char t

Easily measure, record, and detect changes in the transfer of visual information when the change affects only visual acuity at low contrast levels.

Charts include the following contrast levels: black, 25%, 10%, 5%, 2.5%, and 1.25%.

Each chart includes recording forms and instructions. 6 pages, 8.25 cm x 22.9 cm.

$95.00

Pacific Acuity Test The Pacific Acuity Test is a vanishing optotype test It is designed with opposing figures to provide a

simple forced-choice testing format. It is appropriate for nonverbal children and

individuals with developmental disabilities who are unable to respond to standard optotype recognition tests.

Each card has two figures, a simple face, and an opposing oval target of the same overall size but with interior details that allow discrimination from the face at the threshold of acuity.

Pacific Acuity Test

$680.00

Pacific Acuity Test The full test kit consists of 18 cards with two cards

at each level. The cards at each acuity level have a different

position of the face target compared to the opposing oval figure.

Each card can be presented at either 50 cm or 1 meter

But the 1 meter test distance is recommended for greater accuracy and comparison to distance visual acuity tests.

The test range from 20/400 down to 20/20 allows for testing a broad range of visual acuity

Cardiff Pediatric Low Contrast Charts Cardiff Low Contrast Charts are designed to measure

contrast sensitivity in developing toddlers and young children, as well as in older children and adults with intellectual

impairment.

Test targets are pictures of the same size that decrease in contrast between light and dark bands.

The contrast sensitivity is determined by the faintest bands for which the target is visible.

The test covers 12 contrast levels using 3 cards at each level (36 cards total) using the preferential looking technique.

Cardiff Pediatric Low Contrast Charts Contrast levels begin at 46% and decrease to 1%, which

equates to sensitivity levels of 2.17 to 100. Cardiff Low Contrast Chart test is conducted at distance of 50 cm, the targets represent 1.9 cpd (6/90) distance of 1 m the targets represent 3.8 cpd(6/45). distance of 25 cm the targets represent 1.0 cpd (6/180).

$1,650.00

Hiding Heidi Low Contrast Face Test

Visual communication is the most important communication method during the first year of life.

The ability to detect objects of low contrast is an important component of the visual system.

For example, facial expressions are mediated by faint shadows and changes in the contours of the mouth and eyes.

Hiding Heidi Low Contrast Face Test

Determining the levels of contrast that an infant can detect helps provide baseline data for evaluating future changes.

For example, deviations from usual behavior may indicate disorders that leave vision at high-contrast levels unaffected.

Four cards printed on both sides in the following contrast levels: black, 25%, 10%, 5%, 2.5%, and 1.25%.

Cards are 23 cm x 23 cm$95.00

Computer/Video Contrast Sensit ivity Testing

Computer/video grating tests offer the highest degree of test flexibility in terms of technique, target configuration, and spatial frequencies.

The disadvantage to to these systems is that they are relatively costly and complex.

They also require careful consideration and monitoring of contrast calibration of the video display.

Enhancement game

The enhancement game is the first game that allows training of low contrast vision in play situation.

It is used for young children & multihandicapped persons.

It is useful to enhance and train visual function at low contrast levels in amblyopic eye.

The Pelli-Robson”* variable contrast letter chart consists of 16 groups of three letters (a ‘triplet’) arranged on eight lines.

The contrast of each triplet reduces in logarithmic steps. As the letter size (spatial frequency) is fixed and the contrast is varied the test procedure is more like conventional contrast sensitivity measurement.

As the patient reads down the chart the letters reduce in contrast and in contrast sensitivity terms they move up Figure 2 until the detection limit is reached near the peak’of the CSF.

In the manufacturer’s description and in most reports the test is administered at one metre and would be expected to measure sensitivity at approximately one cycle per degree (fundamental frequency) but higher harmonics (3, 5 and 7 c.p.d.) will also be detected.

We suggest that the test may be better at three or four metres, where the fundamental spatial frequency tested is approximately three or four cycles per degree45 and therefore nearer the peak of the CSF.

In the original description of the test, the last triplet where at least two letters are read correctly is scored.32

To improve reliability, Elliott and colleaguesg2 suggested scoring correct a call of ‘C’ for ‘0’ or a call of ‘0’ for ‘C’.

To further improve reliability, theyg3 then suggested scoring each correct letter as 0.05 units.

At one metre, the average Pelli-Robson score should reduce from about 1.90-l 85 at age 20 to 30 years to about 1.80-l .75 at age 70 years.5g~94~95

If a different distance such as three metres is used, ‘normal’ values will need to be established.

Lighting requirements of 85 cd/m2 (acceptable range 60 to 120 cd/m*) can require some manipulation to get this large (64 x 85 cm) chart

evenly lit. Pelli-Robson charts have proven to be quick and reliable in clinical

practice and to have significant uses in the description of visual performance.

Studies by a number of workers have demonstrated that the Pelli-Robson chart can detect a reduction in visual function in patients

The two main types of CS charts are in use; charts that show gratings, such as the Functional Acuity Contrast Test (FACT) charts (as it is used in the OPTEC Functional Vision Analyzer, Stereo Optical, IL, USA),[8] and charts that show letters, either with altering optotype size at constant contrast settings (e.g., 5 or 10% contrast) or optotypes that are always of the same size but with decreasing contrast levels, such as the Pelli Robson